[Tex/LaTex] Citation with only a number between bracket

Question

I cannot figure out how to make my citations appear with a simple number between brackets, like [1].
I obtain: "author et al. [year]"
I use the documentclass book with natbib-package.

Edit1:
I tried \citet{key} instead of \cite{}, it has no effect.

Answer 1

You haven't specified which bibliography style you use. Assuming it's a style that can generate both numeric-style and authoryear-style citation call-outs -- some bibliography styles can generate only the latter type... -- you should load the natbib package with the option numbers. Alternatively, issue the instruction

\setcitestyle{numbers}

after loading the natbib package.